Allergies to drugs, foods, and aeroallergens affect both children and adults across the world. Highly sensitive and specific in vitro methods that are efficient and easy to use to identify relevant food, drug, and/or aero allergens are lacking. Our group has recently developed comprehensive flow cytometry-based protocols for the analysis of surface markers in basophil populations in small amounts of human whole blood. We propose to use the basophils contained in whole blood to assess the presence of drug, aero, and/or food allergy. The assay could potentially have a long term, powerful impact to diagnose and follow subjects with food, drug, and/or aeroallergen allergy. Our approach will include using small amounts of whole blood samples from well characterized controls and from drug, aeroallergen, and food allergic subjects who are well characterized and who we have already been challenged with drug, aeroallergen and/or food in the Stanford Hospitals and Clinics to document their allergen reactivity. We hypothesize that our innovative exploratory whole blood assay in which basophils are characterized by measuring their expression of extracellular antigens, like CD203c and CD63, represents a potentially better approach for the assessment and clinical monitoring of drug, aeroallergen and food allergy. Specifically, our overall aim includes: to determine whether the presence of an allergy can be revealed by our novel assay using small amounts of whole blood to measure basophil activation stimulated by ex vivo challenge with purified candidate allergens for 20 minutes. Our overall objective is to obtain data over the next 2 years, using these whole blood assays, which will permit us to chart the ability of the diagnostic allergy test (or DAT) to accurately diagnose food, drug, or aero allergies.